Pluto has been puzzling us with its weirdly smooth surface, but if it’s the first Kuiper Belt Object we’ve visited, how did we know how many craters to expect in the first place? Here’s everything we’ve figured out about collisions in this chaotic area of our Solar System. »7/28/15 8:32pm Tuesday 8:32pm

On the 23rd and 24th of January, 1930, a young astronomer working in Flagstaff, Arizona, scanned a small patch of the night sky. He was taking pictures of star positions, looking for anomalies that would signal movement somewhere at the edge of the solar system. He took the pictures then set them aside, not realizing… »7/12/15 4:25pm 7/12/15 4:25pm

Scientists are mulling over which of two icy bodies NASA's New Horizons spacecraft should visit following its Pluto encounter this summer — provided the U.S. space agency comes up with funding for an extended mission. »3/22/15 1:48pm 3/22/15 1:48pm